Try this-
Use the service name to delete the service.And place that name within double quotes.
Also, it is possible that you might be using the display name of the service to delete it, sometimes it is different from the service name.
Hope it helps.

Another way through regway. Before performing please take a backup of reg key.
Go to HKLM\System\CurrentControlServices\services\ and search for your Service Key. delete the key, reboot . this should help you out.